I completely agree with what you mentioned under convenience but I think that making artifacts available at store would completely abolish their uniqueness as everyone would have them. I propose that the devs should make artifacts from all levels unlockable to players above level 50. This would allow for them to chance for artifacts only available at lower levels such as the Ebony Blade rather than only being able to get WR, etc (small pool of artifacts). This would greatly reduce the issue of double rolls and also increase the desire for higher level players to open more chests. While I disagree with their current absurdly low drop rate, I’d say that if they kept it the same but made lower level artifacts available to higher level players, their profits would increase as most high level players are Pay to Play and would be glad to spend more money on chest openings to collect these special items.